Identify Analysis pass.

Do not run analysis pass again if analysis info is still available.
This fixes PR1441.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48476 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -68,6 +68,9 @@ class MemoryDependenceAnalysis : public FunctionPass {
     static char ID; // Class identification, replacement for typeinfo
     MemoryDependenceAnalysis() : FunctionPass((intptr_t)&ID) {}
 
+    /// isAnalysis - Return true if this pass is  implementing an analysis pass.
+    virtual bool isAnalysis() const { return true; }
+
     /// Pass Implementation stuff.  This doesn't do any analysis.
     ///
     bool runOnFunction(Function &) {return false; }